Method for reducing formation of polychlorinated aromatic compounds during air oxychlorination of C1 -C3 Hydrocarbons

Abstract

An improved process is disclosed for manufacturing chlorinated hydrocarbon by way of a once-through air-based oxychlorination process which yields reduced levels of environmental toxins such as chlorobenzenes, polychlorinated biphenyls, polychlorinated dibenzodioxins and polychlorinated dibenzofurans. The process involves fixed bed or fluid bed catalyzed oxychlorination of a hydrocarbon reactant containing from 1 to 3 carbon atoms. The oxychlorination process consists of contacting the hydrocarbon reactant with air or oxygen enriched air and hydrogen chloride in the presence of the oxychlorination catalyst in a heated reaction zone operated at from 150° C. to 600° C. and recovering chlorinated hydrocarbon from the effluents of the reaction zone. The improvement consists of the use of air which is pretreated before use in the operated oxychlorination process by a means for removal of the aromatic hydrocarbons.

We claim: 
     
       1. An improved process for manufacturing chlorinated hydrocarbon with reduced formation of chlorobenzenes, polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), said process starting with C 1  to C 3  hydrocarbon reactant selected from the group consisting of methane, ethane, ethylene, acetylene, propane, propylene, methylacetylene, and halogen substituted versions thereof, said process comprising: contacting said reactant with air or oxygen enriched air and hydrogen chloride, said contacting is conducted in the presence of a copper (II) oxychlorination catalyst in a heated reaction zone operating at from 150° C. to 600° C. wherein chlorinated hydrocarbon is recovered from the effluents of the reaction zone, the process is characterized by the fact that the air is pretreated with a means for removal of aromatic hydrocarbons. 
     
     
       2. The process of claim 1 wherein said means for removal of aromatic compounds from air is selected from the group consisting of distillation, adsorption, absorption, hydrogenation, and oxidation. 
     
     
       3. The process of claim 1 wherein said means for removal of aromatic compounds is selected from the group consisting of (a) passing said air through a vessel containing activated carbon,   (b) treating said air with activated charcoal,   (c) treating said air with silica,   (d) treating said air with an aromatic compound adsorptive resin,   (e) subjecting said air to a hydrogenation process,   (f) extraction of said air with aliphatic liquid hydrocarbon, and   (g) subjecting said air to an oxidation process.   
     
     
       4. The process of claim 1 wherein said hydrocarbon is selected from the group consisting of methane, ethane and propane and wherein said heated reaction zone is operated at from 300° C. to 600° C. 
     
     
       5. The process of claim 1 wherein said hydrocarbon is selected from the group consisting of ethylene, acetylene, propylene, and methylacetylene and wherein said heated reaction zone is operated at from 150° C. to 300° C. 
     
     
       6. The process of claim 1 wherein said hydrocarbon is ethylene.